Chairs commonly used involve a seat of such length, average 17 inches, but often up to 20 inches or more, such that the user bears weight on the buttocks and ischia as well as the thighs. (When is the last time you considered sitting on your thighs? . . . So, why do we?) Such a design puts pressure on the user's thighs and calves, affecting circulation to the legs and feet, and creating discomfort for the user. The lumbar spine is encouraged into a position of extreme flexion known to create disc pathology, another source of much pain and lost work time.
The user may attempt relief by shifting the hips forward into a sacral sit position in which weight is borne through the apex of the sacrum and through the tailbone. While this position relieves strain on the thighs and calves, it also creates a more extreme flexion strain of the lumbar spine.
An alternate solution often used is the lumbar roll. A look at any anatomical chart or specimen by layman or professional alike reveals an acute angle of the lower lumbar spine at L5-S1. The lordotic angle of the mid to upper lumbar spine is much more gradual. A lumbar roll provides a uniform angle for the whole lumbar spine thus providing either too sharp an angle for the upper and mid lumbar spine or too obtuse an angle for the lower lumbar spine.
Should a user find comfort and good bio-mechanics sitting in a standard task chair, yet remains the difficulty in sustaining it while working at a desk. In a standard task chair it is necessary to lean forward to work at a desk thus losing the benefit of the lumbar support available. This option places the user's upper body in a position of strain contributing to headaches, shoulder, neck and mid-back pain, and double crush injuries contributing to carpal tunnel syndrome. The user may alternately choose to sit at the edge of the chair abandoning the lumbar support altogether. Most users lack the ability to sustain an unsupported upright position for any prolonged period thus leaving the user's upper body in a position of strain such as previously described.
Any attempt to modify seating as we know it, should take into consideration the social value of the chair. Sitting in a chair is valued as an adult and civilized behavior in Western societies. The boss sits in a wide chair with a high back, often of leather while supportive staff sit in low backed chairs, which are narrower and usually not of leather. (Ref. “The Chair” by Galen Cranz, W.W. Norton Company Inc, 1998) To remove these options in seating by using a stool, a kneeling chair, or a saddle, a users value system and expectations are compromised.
There is a need for a chair that maintains the expected social variations while providing any user with an anatomically supportive, ergonomic seating position.